1. Field of the Invention
The present invention relates to a display illumination structure.
2. Description of the Related Art
An instrument panel is disposed at a front portion of a passenger compartment in a vehicle such as a motor vehicle. Instruments that display vehicle speed, engine speed and other driver information are provided in portions of the instrument panel which are situated in front of a driver's seat and between the driver's seat and a front passenger's seat (for example, refer to JP-A-2011-47790).
These instruments are equipped with displays for displaying the aforesaid various types of driver information, and these displays can be illuminated.
FIG. 5 shows a sectional view of an instrument system 1 like those described above. This instrument system 1 includes a display 3 having a translucent lighting type gauge portion 2 (not shown in detail) which can be backlit. Additionally, a light source 4 is provided on a back surface side of the display 3. Further, a light guiding member 5 is provided which guides light L emanating from the light source 4 to at least a back surface side of the gauge portion 2 of the display 3.
The display 3 is disposed on a front surface side of a housing 6. Additionally, the light source 4 and the light guiding member 5 are disposed and accommodated in an interior of the housing 6. The housing 6 has on an inner surface thereof a reflecting surface 7 which reflects the light L that exits from the light guiding member 5 so as to be returned to the light guiding member 5.
Additionally, the light guiding member 5 has at least an incident portion 8 on which light L emanating from the light source 4 is incident and a horizontally extending portion 9 which guides the light L emanating from the light source 4 along the gauge portion 2 of the display 3 and further has an interior reflecting bent portion 11 which reflects the light L that enters from, the incident portion 8 towards the horizontally extending portion 9.
It should be noted that the light source 4 is mounted on a substrate 12 which is placed on a back surface side of the housing 6. Additionally, an embossed, fine irregular or microdot illumination adjusting portion 13 is formed on a back surface side of the light guiding member 5 (or at least the horizontally extending portion 9 thereof) to reflect or diffuse part of the light L guided into an interior of the light guiding member 5 so as to intensify the illumination at part of the gauge portion 2.
According to this configuration, the following advantage can be obtained.
Namely, the light L emanating from the light source 4 enters the interior of the light guiding member 5 from the incident portion 8. The light L that has entered the light guiding member 5 is reflected by the interior reflecting bent portion 11 in the interior of the light guiding member 5 and is then guided to the horizontally extending portion 9. The light L that has been guided to the horizontally extending portion 9 is guided towards a distal end portion of the horizontally extending portion while being reflected on the reflecting surface 7 formed on the housing 6, and part thereof is reflected or diffused at the illumination adjusting portion 13 for use in illuminating the gauge portion 2 of the display 3.
However, the display illumination structure has the following problems.
Namely, the interior reflecting bent portion 11 of the light guiding member 5 is configured so that the light L is bent by the reflecting surface having a reflection angle (a critical angle) at which the light L is totally reflected and formed on an outer circumferential surface side or an upper surface side, as seen in the figure, of the horizontally extending portion 9 so that the light L is allowed to reach a distal end of the horizontally extending portion 9. This makes it difficult for the light L to reach near the light source 4, causing the tendency to produce a low-luminance poorly illuminated portion 14 in a position on the gauge portion 2 which lies closer to the light source 4 or the like.
In this way, when the low-luminance poorly illuminated portion 14 is produced in the position on the gauge portion 2 which lies closer to the light source 4 or the like, the gauge portion 2 cannot be provided so as to extend as near as the light source 4, this causing problems that the range where the gauge portion 2 can be placed gets narrow and that the degree of freedom in designing the display 3 gets small.